In general, mounted at one end of the steering shaft connected to the steering gear, a steering wheel of a vehicle allows the wheels to turn by transmitting the amount of its turning to the steering gear through the steering shaft and is made of a light-weight material, such as PVC or urethane, to improve steering performance of a driver.
A common steering wheel 1, as shown in FIG. 1, is completed as a product by forming a synthetic resin part 4 around a frame 2 of steel or light alloy by foaming of a synthetic resin (polyurethane). The surface of the steering wheel coated with synthetic resin part 4 is hard and slippery, such that the driver may easily feel tired in steering, which may occur an accident may. Therefore, in order to overcome the problems, a product with a leather cover sewn or bonded around the outside of synthetic resin part 4 has been manufactured.
In detail, as shown in FIG. 2A, a steering wheel is completed as the following processes: first, inserting a frame 2 composed of a rim 2a and spokes 2b into a foaming mold M as shown in FIG. 2B; forming synthetic resin part 4 of a polyurethane foaming body by foaming polyurethane (polyol, isocyanate hardener, and catalyst), and then sewing or bonding a leather cover around the outside of synthetic resin part 4.
However, the steering wheel and a method of manufacturing the steering wheel as described above had problems that since polyurethane is foamed with frame 2 inserted in foaming mold M to form a synthetic resin part of a foamed body, the manufacturing cost for the product increases because excessive amounts of polyurethane and manufacturing processes, and since the foamed body is formed with the frame, it is difficult to recycle the parts separated.